How do I get count in MongoDB based on specific fields - node.js

Question

I have documents like this in my MongoDB Listings collection.
listingID: 'abcd',
listingData: {
category: 'resedetial'
},
listingID: 'xyz',
listingData: {
category: 'resedetial'
},
listingID: 'efgh',
listingData: {
category: 'office'
}
I am trying to get total count of all listings and count according to category.
I can get total count of listings with aggregation query. But I am not sure how to get output like this resedentialCount: 2, officeCount: 1 , ListingsCount: 3
This is my aggregation query
{
$match: {
listingID,
},
},
{
$group: {
_id: 1,
ListingsCount: { $sum: 1 },
},
}

Answer 1

Try this:
let listingAggregationCursor = db.collection.aggregate([
{$group: {_id:"$listingData.category",ListingsCount:{$sum:1} }}
])
let listingAggregation=await listingAggregationCursor.toArray();
(I got this query from https://www.statology.org/mongodb-group-by-count)
This will give you an array of objects with each listing category as well as how many times they occur.
For getting the total listingsCount, sum up all of the count fields from the array of objects. You can do that like this:
let listingsCount=0;
for(listingCategory of listingAggregation) {
listingsCount+=listingCategory.count;
}
You should have the data you need at this point. Now it's just a matter of extracting and formatting it as you see fit.
Hope this helps!